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Add GeoJsonParser
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‎openmapview/src/main/kotlin/de/afarber/openmapview/GeoJsonParser.kt‎

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/*
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* Copyright (c) 2025 Alexander Farber
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* SPDX-License-Identifier: MIT
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*
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* This file is part of the OpenMapView project (https://github.com/afarber/OpenMapView)
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*/
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package de.afarber.openmapview
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import android.graphics.Color
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import org.json.JSONArray
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import org.json.JSONObject
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/**
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* Parser for GeoJSON data to convert to map overlays.
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*
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* Supports GeoJSON Feature, FeatureCollection, and direct geometries:
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* - Point -> Marker
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* - LineString -> Polyline
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* - Polygon -> Polygon
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* - MultiPoint -> Multiple Markers
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* - MultiLineString -> Multiple Polylines
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* - MultiPolygon -> Multiple Polygons
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*/
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object GeoJsonParser {
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/**
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* Parse GeoJSON string and return parsed features.
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*
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* @param geoJsonString Valid GeoJSON string
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* @return GeoJsonResult containing markers, polylines, and polygons
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*/
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fun parse(geoJsonString: String): GeoJsonResult {
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val json = JSONObject(geoJsonString)
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return parseGeoJson(json)
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}
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private fun parseGeoJson(json: JSONObject): GeoJsonResult {
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val type = json.optString("type", "")
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return when (type) {
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"FeatureCollection" -> parseFeatureCollection(json)
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"Feature" -> parseFeature(json)
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"Point", "MultiPoint" -> parseGeometry(json, null)
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"LineString", "MultiLineString" -> parseGeometry(json, null)
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"Polygon", "MultiPolygon" -> parseGeometry(json, null)
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else -> throw IllegalArgumentException("Unsupported GeoJSON type: $type")
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}
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}
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private fun parseFeatureCollection(json: JSONObject): GeoJsonResult {
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val features = json.optJSONArray("features") ?: return GeoJsonResult()
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val markers = mutableListOf<Marker>()
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val polylines = mutableListOf<Polyline>()
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val polygons = mutableListOf<Polygon>()
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for (i in 0 until features.length()) {
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val feature = features.getJSONObject(i)
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val result = parseFeature(feature)
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markers.addAll(result.markers)
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polylines.addAll(result.polylines)
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polygons.addAll(result.polygons)
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}
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return GeoJsonResult(markers, polylines, polygons)
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}
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private fun parseFeature(json: JSONObject): GeoJsonResult {
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val geometry = json.optJSONObject("geometry") ?: return GeoJsonResult()
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val properties = json.optJSONObject("properties")
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return parseGeometry(geometry, properties)
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}
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private fun parseGeometry(
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geometry: JSONObject,
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properties: JSONObject?,
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): GeoJsonResult {
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val type = geometry.optString("type", "")
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val coordinates = geometry.optJSONArray("coordinates") ?: return GeoJsonResult()
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return when (type) {
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"Point" -> parsePoint(coordinates, properties)
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"MultiPoint" -> parseMultiPoint(coordinates, properties)
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"LineString" -> parseLineString(coordinates, properties)
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"MultiLineString" -> parseMultiLineString(coordinates, properties)
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"Polygon" -> parsePolygon(coordinates, properties)
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"MultiPolygon" -> parseMultiPolygon(coordinates, properties)
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else -> throw IllegalArgumentException("Unsupported geometry type: $type")
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}
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}
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private fun parsePoint(
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coordinates: JSONArray,
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properties: JSONObject?,
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): GeoJsonResult {
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val latLng = parseCoordinate(coordinates)
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val marker =
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Marker(
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position = latLng,
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title = properties?.optString("name") ?: properties?.optString("title"),
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snippet = properties?.optString("description"),
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)
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return GeoJsonResult(markers = listOf(marker))
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}
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private fun parseMultiPoint(
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coordinates: JSONArray,
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properties: JSONObject?,
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): GeoJsonResult {
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val markers = mutableListOf<Marker>()
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for (i in 0 until coordinates.length()) {
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val coord = coordinates.getJSONArray(i)
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val latLng = parseCoordinate(coord)
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val marker =
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Marker(
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position = latLng,
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title = properties?.optString("name") ?: properties?.optString("title"),
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snippet = properties?.optString("description"),
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)
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markers.add(marker)
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}
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return GeoJsonResult(markers = markers)
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}
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private fun parseLineString(
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coordinates: JSONArray,
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properties: JSONObject?,
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): GeoJsonResult {
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val points = parseCoordinateArray(coordinates)
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if (points.size < 2) return GeoJsonResult()
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val polyline =
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Polyline(
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points = points,
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strokeColor = parseColor(properties?.optString("stroke")) ?: Color.BLUE,
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strokeWidth = properties?.optDouble("stroke-width", 5.0)?.toFloat() ?: 5f,
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tag = properties,
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)
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return GeoJsonResult(polylines = listOf(polyline))
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}
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private fun parseMultiLineString(
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coordinates: JSONArray,
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properties: JSONObject?,
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): GeoJsonResult {
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val polylines = mutableListOf<Polyline>()
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for (i in 0 until coordinates.length()) {
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val lineCoords = coordinates.getJSONArray(i)
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val points = parseCoordinateArray(lineCoords)
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if (points.size >= 2) {
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val polyline =
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Polyline(
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points = points,
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strokeColor = parseColor(properties?.optString("stroke")) ?: Color.BLUE,
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strokeWidth = properties?.optDouble("stroke-width", 5.0)?.toFloat() ?: 5f,
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tag = properties,
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)
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polylines.add(polyline)
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}
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}
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return GeoJsonResult(polylines = polylines)
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}
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private fun parsePolygon(
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coordinates: JSONArray,
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properties: JSONObject?,
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): GeoJsonResult {
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if (coordinates.length() == 0) return GeoJsonResult()
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// First array is outer ring
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val outerRing = parseCoordinateArray(coordinates.getJSONArray(0))
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if (outerRing.size < 3) return GeoJsonResult()
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// Remaining arrays are holes
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val holes = mutableListOf<List<LatLng>>()
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for (i in 1 until coordinates.length()) {
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val hole = parseCoordinateArray(coordinates.getJSONArray(i))
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if (hole.size >= 3) {
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holes.add(hole)
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}
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}
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val polygon =
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Polygon(
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points = outerRing,
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holes = holes,
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strokeColor = parseColor(properties?.optString("stroke")) ?: Color.BLACK,
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strokeWidth = properties?.optDouble("stroke-width", 3.0)?.toFloat() ?: 3f,
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fillColor = parseColor(properties?.optString("fill")) ?: Color.argb(100, 128, 128, 128),
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tag = properties,
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)
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return GeoJsonResult(polygons = listOf(polygon))
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}
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private fun parseMultiPolygon(
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coordinates: JSONArray,
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properties: JSONObject?,
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): GeoJsonResult {
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val polygons = mutableListOf<Polygon>()
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for (i in 0 until coordinates.length()) {
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val polygonCoords = coordinates.getJSONArray(i)
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val result = parsePolygon(polygonCoords, properties)
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polygons.addAll(result.polygons)
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}
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return GeoJsonResult(polygons = polygons)
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}
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private fun parseCoordinate(coordinates: JSONArray): LatLng {
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val lng = coordinates.getDouble(0)
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val lat = coordinates.getDouble(1)
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return LatLng(lat, lng)
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}
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private fun parseCoordinateArray(coordinates: JSONArray): List<LatLng> {
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val points = mutableListOf<LatLng>()
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for (i in 0 until coordinates.length()) {
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val coord = coordinates.getJSONArray(i)
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points.add(parseCoordinate(coord))
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}
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return points
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}
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private fun parseColor(colorString: String?): Int? {
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if (colorString == null) return null
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return try {
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Color.parseColor(colorString)
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} catch (e: IllegalArgumentException) {
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null
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}
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}
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}
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/**
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* Result of parsing GeoJSON data.
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*/
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data class GeoJsonResult(
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val markers: List<Marker> = emptyList(),
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val polylines: List<Polyline> = emptyList(),
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val polygons: List<Polygon> = emptyList(),
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)

‎openmapview/src/main/kotlin/de/afarber/openmapview/MapController.kt‎

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fun getPolygons(): List<Polygon> = polygons.toList()
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fun addGeoJson(geoJsonString: String): GeoJsonResult {
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val result = GeoJsonParser.parse(geoJsonString)
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result.markers.forEach { addMarker(it) }
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result.polylines.forEach { addPolyline(it) }
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result.polygons.forEach { addPolygon(it) }
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return result
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}
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fun handleMarkerTouch(
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x: Float,
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y: Float,

‎openmapview/src/main/kotlin/de/afarber/openmapview/OpenMapView.kt‎

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fun getPolygons(): List<Polygon> = controller.getPolygons()
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fun addGeoJson(geoJsonString: String): GeoJsonResult {
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val result = controller.addGeoJson(geoJsonString)
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invalidate()
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return result
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}
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fun setOnAttributionClickListener(listener: () -> Unit) {
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attributionOverlay.onAttributionClickListener = listener
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}

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